Field of Invention
This invention relates to a tugger train trailer having an adjustable-height support frame or support frame part.
Description of Related Art
Tugger train trailers of this type are increasingly used in the automated series manufacturing of products, such as motor vehicles, for example, where the individual work stations are supplied with the necessary components by means of tugger trains or trailer trains. In a trailer train, a traction vehicle tows a plurality of tugger train trailers on which the required individual parts are transported. As a rule, these parts are delivered on pallets or in wire mesh boxes which are moved over short distances on transport cars (trolleys).
The invention is based on tugger train trailers with support frames, all or part of which can be lifted by means of built-in lifting devices relative to the wheels of the chassis to prevent the steering wheels of the trolley from rolling on the floor during transport inside the plant and negatively affecting the traction behavior. Examples of this prior art are disclosed in European Patent EP 2 161 182 B1 that includes a support frame that is in the shape of an E when viewed from overhead and German utility model DE 20 2009 001 933 U1 that includes a C-shaped support frame.
EP 2 808 234 A1 describes a variant in which, to lift the trolley, the entire support frame is not moved vertically but only a part of it, in this case a center bracket on which the trolley is supported.
It is known that pneumatic or hydraulic work cylinders can be used for the lifting device. However, pneumatic lifting mechanisms require a compressor that demands a great deal of energy and has the additional disadvantage that it is relatively noisy. Hydraulic lifting mechanisms have a significantly higher efficiency than pneumatic lifting mechanisms although they also have the disadvantage that the hydraulic medium is oil, which results in major contamination in the event of leaks.
Therefore, the transition is frequently made to lifting devices that have electrically driven spindles, although satisfactory levels of efficiency cannot be achieved on account of friction losses in the thread.